Data Assimilation of the Stereo Reconstructed Wave Fields to a Nonlinear Phase Resolved Wave Model

2019 ◽  
Author(s):  
Shogo Watanabe ◽  
Wataru Fujimoto ◽  
Tak Nose ◽  
Tsubasa Kodaira ◽  
Graham Davies ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Wave Field ◽  
Wave Model ◽  
Stereo Imaging ◽  
Stereo Images ◽  
Sagami Bay ◽  
Wave Fields ◽  
Stereo Camera ◽  
Significant Wave ◽  
Reconstructed Wave

Abstract A stereo camera system was installed facing Southeast at the observational tower owned by the University of Tokyo in the Sagami Bay, Japan. The three-dimensional wave fields were reconstructed from the stereo images, which were successfully captured from April 2017 until now, by using an open source software WASS (Waves Acquisition Stereo System). The significant wave heights and periods calculated from the stereo images covering an area of 80 m by 80 m were compared against those derived from the ultra-sonic wave gauge at the tower. Overall, a reasonable agreement is achieved, but the accuracy of the stereo reconstruction degrades with the distance from the camera. Also, the significant wave period derived from stereo imaging tends to be shorter, likely related to the error at high frequencies. The reconstructed wave field will be assimilated into a phase-resolved nonlinear wave model. The ensemble Higher Order Spectral simulations and the implementation of the a4DVAR data assimilation scheme, allowed us to substantially extend the estimated wave field beyond the stereo imaging domain. A field campaign with an ADCP in the field of view of the stereo camera and two surface wave buoys outside of the view were conducted for validation.

Application of Data Assimilation for a Spectral Wave Model on Unstructured Meshes

2006 ◽  
Author(s):  
Tai-Wen Hsu ◽  
Shan-Hwei Ou ◽  
Jian-Ming Liau ◽  
Jaw-Guei Lin ◽  
Chia-Chuen Kao ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Wind Wave ◽  
Wave Spectrum ◽  
Wave Model ◽  
Wave Period ◽  
Optimal Interpolation ◽  
Sequential Method ◽  
Significant Wave ◽  
Spectral Wave Model ◽  
Buoy Data

The effect of the data assimilation of buoy data in the wind wave model (WWM) for wind wave simulations in both deep and shallow water regions developed by Hsu et al. [2005] is investigated. Following Lionello et al. [1992], the sequential method is implemented, where analyzed wave spectra and significant wave fields were assimilated by optimal interpolation (OI), then the analyzed values were used to reconstruct the wave spectrum. This paper examines the results of the assimilation of wave spectrum, significant wave height and significant wave period in a nearshore WWM model. The WWM model underestimates the wave period because it incorrectly applies past wave field data. The analysis has provided useful indications of the shortcomings of the WWM model. In summary, the OI approach is shown to be a reliable assimilation scheme in the WWM model.

scholarly journals Directional Coherent Wave Group From an Assimilated Non-linear Wavefield

2021 ◽  
Vol 9 ◽  
Author(s):  
Takuji Waseda ◽  
Shogo Watanabe ◽  
Wataru Fujimoto ◽  
Takehiko Nose ◽  
Tsubasa Kodaira ◽  
...  
Keyword(s):  
Wave Field ◽  
Wave Model ◽  
Linear Wave ◽  
Wave Group ◽  
Wave Groups ◽  
Radar Images ◽  
Coherent Wave ◽  
Non Linear ◽  
Directional Wave ◽  
Reconstructed Wave

The presence of coherent wave groups in the ocean has been so far postulated but still lacks evidence other than the indication from the radar images. Here, we attempt to reconstruct a wave field to monitor the evolution of a directional wave group based on a phase resolving two-dimensional non-linear wave model constrained by the stereo images of the ocean surface. The reconstructed wave field of around 20 wavelength squared revealed a coherent wave group compact in both propagating and transverse directions. The envelope of the wave group seems to be oriented obliquely to the propagation direction, somewhat resembling the directional soliton that was theoretically predicted and experimentally and numerically reproduced recently. A comparison with a constrained linear wave model demonstrated the coherence of the non-linear wave group that propagates for tens of wavelengths. The study elaborates a possibility of a spatially coherent short crested wave group in the directional sea.

Stereo imaging in the shadow electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 120-121
Author(s):  
W. C. T. Dowell
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Convenient Method ◽  
Patent Application ◽  
Standard Technique ◽  
Stereo Imaging ◽  
Stereo Images ◽  
Specimen Height

Stereo imaging is not new to electron microscopy. Von Ardenne, who first published transmission pairs nearly forty hears ago, himself refers to a patent application by Ruska in 1934. In the early days of the electron microscope von Ardenne employed a pair of magnetic lenses to view untilted specimens but soon opted for the now standard technique of tilting the specimen with respect to the beam.In the shadow electron microscope stereo images can, of course, be obtained by tilting the specimen between micrographs. This obvious method suffers from the disadvantage that the magnification is very sensitive to small changes in specimen height which accompany tilting in the less sophisticated stages and it is also time consuming. A more convenient method is provided by horizontally displacing the specimen between micrographs. The specimen is not tilted and the technique is both simple and rapid, stereo pairs being obtained in less than thirty seconds.

scholarly journals Null modes effect in Rossby wave model

2004 ◽  
Vol 11 (3) ◽  
pp. 281-293
Author(s):  
V. Goncharov ◽  
V. Pavlov
Keyword(s):  
Nonlinear Wave ◽  
Rossby Wave ◽  
Wave Model ◽  
Wave Fields

Abstract. The problem of the null-modes existence and some particularities of their interaction with nonlinear vortex-wave-like structures is discussed. We show that the null-modes are fundamental elements of nonlinear wave fields. The conditions under which null-modes can manifest themselves are elucidated. The Rossby-Hasegawa-Mima (RHM) model is used for the illustration of features of null-modes-waves interactions.

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

2013 ◽  
Vol 558 ◽  
pp. 489-500 ◽  
Author(s):  
Patrick Norman ◽  
Claire Davis ◽  
Cédric Rosalie ◽  
Nik Rajic
Keyword(s):  
Wave Field ◽  
Lamb Waves ◽  
Base Material ◽  
Adhesive Layer ◽  
Scattered Wave ◽  
Phase Lag ◽  
Wave Fields ◽  
Surface Mount ◽  
Frequency Regime ◽  
Fibre Bragg Gratings

The application of Lamb waves to damage and/or defect detection in structures is typicallyconfined to lower frequencies in regimes where only the lower order modes propagate in order to simplifyinterpretation of the scattered wave-fields. Operation at higher frequencies offers the potentialto extend the sensitivity and diagnostic capability of this technique, however there are technical challengesassociated with the measurement and interpretation of this data. Recent work by the authorshas demonstrated the ability of fibre Bragg gratings (FBGs) to measure wave-fields at frequencies inexcess of 2 MHz [1]. However, when this work was extended to other thinner plate specimens it wasfound that at these higher frequencies, the cyanoacrylate adhesive (M-Bond 200) used to attach theFBG sensors to the plate was significantly affecting the propagation of the waves. Laser vibrometrywas used to characterise the wave-field in the region surrounding the adhesive and it was found that theself-adhesive retro-reflective tape applied to aid with this measurement was also affecting the wavefieldin the higher frequency regime. This paper reports on an experimental study into the influence ofboth of these materials on the propagating wave-field. Three different lengths of retro-reflective tapewere placed in the path of Lamb waves propagating in an aluminium plate and laser vibrometry wasused to measure the wave-field upstream and downstream of the tape for a range of different excitationfrequencies. The same experiment was conducted using small footprint cyanoacrylate film samplesof different thickness. The results show that both of these surface-mount materials attenuate, diffractand scatter the incoming waves as well as introducing a phase lag. The degree of influence of thesurface layer appears to be a function of its material properties, the frequency of the incoming waveand the thickness and footprint of the surface layer relative to the base material thickness. Althoughfurther work is required to characterise the relative influence of each of these variables, investigationsto date show that for the measurement of Lamb Waves on thin structures, careful considerationshould be given to the thickness and footprint of the adhesive layer and sensor, particularly in the highfrequency regime, so as to minimise their effect on the measurement.

scholarly journals Non-linear wave data assimilation with an ANN-type wind-wave model and Ensemble Kalman Filter (EnKF)

2010 ◽  
Vol 34 (8) ◽  
pp. 1984-1999 ◽  
Author(s):  
Ahmadreza Zamani ◽  
Ahmadreza Azimian ◽  
Arnold Heemink ◽  
Dimitri Solomatine
Keyword(s):  
Kalman Filter ◽  
Data Assimilation ◽  
Ensemble Kalman Filter ◽  
Wind Wave ◽  
Wave Model ◽  
Linear Wave ◽  
Wave Data ◽  
Non Linear

scholarly journals Synergy between satellite observations and model simulations during extreme events

2018 ◽  
Author(s):  
Anne Wiese ◽  
Joanna Staneva ◽  
Johannes Schultz-Stellenfleth ◽  
Arno Behrens ◽  
Luciana Fenoglio-Marc ◽  
...  
Keyword(s):  
Satellite Data ◽  
Extreme Events ◽  
Wave Model ◽  
Coastal Areas ◽  
In Situ Measurements ◽  
Model Simulations ◽  
Significant Wave ◽  
Operational Analysis

Abstract. In this study, the quality of wind and wave data provided by the new Sentinel-3A satellite is evaluated. We focus on coastal areas, where altimeter data are of lower quality than those for the open ocean. The satellite data of Sentinel-3A, Jason-2 and CryoSat-2 are assessed in a comparison with in situ measurements and spectral wave model (WAM) simulations. The sensitivity of the wave model to wind forcing is evaluated using data with different temporal and spatial resolution, such as ERA-Interim and ERA5 reanalyses, ECMWF operational analysis and short-range forecasts, German Weather Service (DWD) forecasts and regional atmospheric model simulations -coastDat. Numerical simulations show that both the wave model forced using the ERA5 reanalyses and that forced using the ECMWF operational analysis/forecast demonstrate the best capability over the whole study period, as well as during extreme events. To further estimate the variance of the significant wave height of ensemble members for different wind forcings, especially during extreme events, an empirical orthogonal function (EOF) analysis is performed. Intercomparisons between remote sensing and in situ observations demonstrate that the overall quality of the former is good over the North Sea and Baltic Sea throughout the study period, although the significant wave heights estimated based on satellite data tend to be greater than the in situ measurements by 7 cm to 26 cm. The quality of all satellite data near the coastal area decreases; however, within 10 km off the coast, Sentinel-3A performs better than the other two satellites. Analyses in which data from satellite tracks are separated in terms of onshore and offshore flights have been carried out. No substantial differences are found when comparing the statistics for onshore and offshore flights. Moreover, no substantial differences are found between satellite tracks under various metocean conditions. Furthermore, the satellite data quality does not depend on the wind direction relative to the flight direction. Thus, the quality of the data obtained by the new Sentinel-3A satellite over coastal areas is improved compared to that of older satellites.

Variational Wave Data Assimilation in a Third-Generation Wave Model

1994 ◽  
Vol 11 (5) ◽  
pp. 1350-1369 ◽  
Author(s):  
Miriam M. De Las Heras ◽  
Gerrit Burgers ◽  
Peter A. E. M. Janssen
Keyword(s):  
Data Assimilation ◽  
Wave Model ◽  
Third Generation ◽  
Wave Data ◽  
Variational Wave

scholarly journals THE BROAD APPLICATION OF A DEPTH INVERSION ALGORITHM BASED ON THE DYNAMIC MODE DECOMPOSITION

2020 ◽  
pp. 50
Author(s):  
Matthijs Gawehn ◽  
Sierd de Vries ◽  
Stefan Aarninkhof
Keyword(s):  
The Netherlands ◽  
Wave Field ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Inversion Algorithm ◽  
Broad Application ◽  
Significant Wave ◽  
Mode Decomposition ◽  
Novel Algorithm

The technological boost of drones and satellites offers new and more flexible platforms for video-based depth inversion. It signals a desire to generate depth estimates on-the-fly, requiring more flexibility and high computational speeds. For this purpose, a novel algorithm was developed, which is based on the Dynamic Mode Decomposition. The analysis of video from three different field-sites in the Netherlands, Australia and US, suggests that 32 s of video are sufficient to correctly capture the significant wave components in the wave-field. It means that DMD-based depth inversion is suited for fast coastal reconnaissance.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/TcE13C1oTKw

Effect of Uni- and Bi-Directional Coupling of Ocean-Met Interaction on Significant Wave Height and Local Wind

2017 ◽  
Author(s):  
Adil Rasheed ◽  
Jakob Kristoffer Süld ◽  
Mandar Tabib
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Surface Wind ◽  
Wave Model ◽  
Ocean Surface ◽  
Observation Data ◽  
Local Wind ◽  
Near Surface ◽  
Significant Wave ◽  
Bidirectional Coupling

Accurate prediction of near surface wind and wave height are important for many offshore activities like fishing, boating, surfing, installation and maintenance of marine structures. The current work investigates the use of different methodologies to make accurate predictions of significant wave height and local wind. The methodology consists of coupling an atmospheric code HARMONIE and a wave model WAM. Two different kinds of coupling methodologies: unidirectional and bidirectional coupling are tested. While in Unidirectional coupling only the effects of atmosphere on ocean surface are taken into account, in bidirectional coupling the effects of ocean surface on the atmosphere are also accounted for. The predicted values of wave height and local wind at 10m above the ocean surface using both the methodologies are compared against observation data. The results show that during windy conditions, a bidirectional coupling methodology has better prediction capability.

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